Primary 6 problem sum 2

Salim used 3 taps to fill an empty rectangular tank with water.If only 1 tap was used,Tap A could fill the empty tank in 3 hours, Tap B could fill it in 4 hours and Tap C could fill the tank in 8 hours.
Salim first turned on Tap B for 10 minutes.then he turned on Tap A and C. One hour later, he turned off all the 3 taps. What fraction of the tank was still empty?

Salim used 3 taps to fill an empty rectangular tank with water.If only 1 tap was used,Tap A could fill the empty tank in 3 hours, Tap B could fill it in 4 hours and Tap C could fill the tank in 8 hours.
Salim first turned on Tap B for 10 minutes.then he turned on Tap A and C. One hour later, he turned off all the 3 taps. What fraction of the tank was still empty?

Well... 10 minutes is a certain fraction of 4 hours (the time it would take "B" to fill it). So you have that much filled.
Add to that the amount that each could do in an hour... 1/3 + 1/4 + 1/8...

Salim used 3 taps to fill an empty rectangular tank with water.If only 1 tap was used,Tap A could fill the empty tank in 3 hours, Tap B could fill it in 4 hours and Tap C could fill the tank in 8 hours.
Salim first turned on Tap B for 10 minutes.then he turned on Tap A and C. One hour later, he turned off all the 3 taps. What fraction of the tank was still empty?

1/24(during 10 minutes)+1/3(1st tap during an hour)+1/4(2nd tap during an hour)+1/8(3rd tap during an hour)=1/24+8/24+6/24+3/24=18/24=3/4 - fraction of the tank was filled;
1-3/4=1/4 (or 0.25) - fraction of the tank was still empty

Well... 10 minutes is a certain fraction of 4 hours (the time it would take "B" to fill it). So you have that much filled.
Add to that the amount that each could do in an hour... 1/3 + 1/4 + 1/8...

Then subtract your result from 1 (= 24/24)

Originally Posted by ihavenonick

1/24(during 10 minutes)+1/3(1st tap during an hour)+1/4(2nd tap during an hour)+1/8(3rd tap during an hour)=1/24+8/24+6/24+3/24=18/24=3/4 - fraction of the tank was filled;
1-3/4=1/4 (or 0.25) - fraction of the tank was still empty